So I bought a ficus microcarpa bonsai from the store 2 month ago and I noticed a problem since then, some leaves turn partially brown and fall while it's still wet not dry, some new growth also falls while still green, it falls at a rate of 1 leave/day.
The prime suspect is the white powder on the leaves, I tried washing it with distilled water but it didn't wash off.
I also checked the roots to see if the plant is root bound or has root rot but I don't think so as you can see in the picture.
So basically I have no idea what I'm doing wrong, this is my first bonsai, I would appreciate the help.
It's kept indoors with humidity between 40%-60% with a temperature range of 22-27 Celsius.
The main source of light is a CFL lamp 150 watts that is kept on for 8 hours a day, the lux reaching the leaves is 3000 lux with no hotspots.
I fertilized it twice a month with 1 gram of npk 20-20-20.
I water it with tap water when the top soil is dry.